The major overall objective is to extend our work on the purification and characterization of a non-specific suppressor factor that we identified as the sheep erythrocyte receptor of peripheral T cells. Sepcificity of the immunoglobulins associated with it; 2) to develop a radioimminoassay (RIA) to this factor using monoclogal antibody to sheep erythrocyte receptors; 3) to utilize the RIA to quantitate immunosuppressive substances in the sera of patients with cancer and with beingn diseases, autoimmune diseases, and viral infections; and 4) to delineate the mechanism of action of the suppressor factor utilizing protein kinase and DNA polymerase. In this regard emphasis will be placed on studying binding kinetics, transfer processes through the cellular membranes as well as any modulating effects of the suppressor factor on the activities of the proteim kinase and DNA polymerase. Theses studies are designed to give a better understanding of the mechanism of action of this suppressor factor, particularly with respect to its function as a feedback regulator of T cell function. It is anticipated that our studies will aid in delineating molecular and immunochemical characteristics of this suppressor factor, more clearly defining its relationship to the E receptor on the surface of T cells. It is also anticipated that our studies may help to determine whether the suppressor factor found in malignant ascites constitutes a regulatory molecule released from T cell surfaces that acts as a negative feedback inhibitor of their growth and function and, which may also be involved in defective T lymphocyte E rosette function associated with autoimmune diseases and cancer.